Original subtitles

(dramatic orchestral music)

- [Narrator] Venus.

At the surface, it's air is 95% carbon dioxide.

The atmospheric pressure is like being 900 meters deep

in Earth's oceans.

It's hotter than anywhere else in the solar system,

except the sun.

And yet, visionary engineers and scientists

are now unveiling daring new strategies

to explore its tortured landscapes,

to sail it's turbulent, upper-level winds,

to imagine altering its very climate.

(intense instrumental music)

They are taking the first steps

towards settling the second planet from the sun.

- [Mission Control] Ignition sequence started.

All engines are started.

We have a liftoff. We have a liftoff.

(indistinct chatter)

(rocket rumbling)

- [Narrator] The early 1970s.

The Space Age was at its peak.

The Apollo astronauts were exploring the moon.

- [Astronaut] Those rocks have been waiting

four and a half billion years for us to come grab 'em.

- [Narrator] Robotic spacecraft had visited Venus ...

(thunder rumbling)

Mars ...

Mercury ...

and Jupiter, with new missions on the drawing boards.

And yet, in those heady days,

America and Europe faced a series of daunting challenges.

The ongoing Cold War ...

unchecked industrial pollution ...

race and class conflict ...

a sudden fuel shortage.

Many thought that only strict Earth preservation

and laws limiting industry could save civilization.

(gentle woodwind music)

Meanwhile, a small cadre of scientists, philosophers

and writers sought answers in farsighted engineering ...

decentralized information systems ...

which later became the internet and cellular networks ...

molecular biology ...

which led to gene sequencing

and the promise of nanotechnology ...

and human expansion into space.

They envisioned moon bases ...

cities on Mars ...

grand orbital habitats.

The so-called space colonies would pioneer

a whole new way of living.

(feverish string music)

Future residents in space would be free to live

by whatever social contracts they chose.

Huge structures assembled by astronauts and robots,

they would draw upon resources on the moon ...

- [Astronaut] Stand by for pitch over. Oh, are we coming in.

- [Narrator] Materials from asteroids ...

and on the free energy of the sun.

These plans consistently overlooked one planet ...

Venus.

Hellishly hot and enveloped in a crushing atmosphere,

how could anyone ever live there?

To some visionary thinkers, Venus held a unique promise,

one that led to one of the most innovative

mission ideas on the books.

(building orchestral music)

A spacecraft carrying astronauts

is bound inward toward the sun.

It slips into low orbit around Venus,

docking with an uncrewed sister ship sent months before.

One will de-orbit, protected by an arrow shell,

as it bleeds speed into heat.

(booming)

A parachute further slows the vehicle.

But it isn't heading for a landing.

Instead of continuing to the surface,

it deploys and inflating envelope,

an airship up to 130 meters in length.

The High-Altitude Venus Operational Concept, HAVOC.

Its crew sales for about 30 Earth days,

navigating in the fast wins,

suspended beneath an inflated envelope of helium gas.

Circling the planet, they deploy probes

to learn about its atmosphere and geology.

They send out a fleet of small robotic balloons

to dip down into the hostile, lower atmosphere.

(dramatic orchestral music)

Their studies complete, the crew ascends

to their transport ship in orbit.

Then, kicked off by a powerful rocket,

they escape Venus's nearly Earth-level gravity

and make the 100-day journey back to Earth.

HAVOC-style missions would set the stage

for a longterm plan to permanently settle Venus.

(atmospheric music)

Though the landscape of Venus

is a hot, high-pressure death trap,

the upper atmosphere could offer safe harbor.

- In the clouds of Venus,

which is 50 kilometers up from the surface,

there is a realm where it's very much Earth-like

in terms of the conditions,

except for the clouds themselves

are made out of concentrated sulfuric acid.

- Of course, you still have no atmosphere with oxygen in it.

You still have the sulfur oxides

that give you sulfuric acid.

So you don't want to go outside without any protection.

But in terms of temperature and pressure,

it's very, very Earth-like.

- So you can imagine sending humans there

and some kind of a balloon platform

or some other floating platform

to explore the clouds of Venus,

and you wouldn't need a pressure suit,

and you wouldn't have to worry

about the thermal environment; it would be quite pleasant.

You would just need some thin protection

from the acid clouds,

and you would need a breathing apparatus,

since it's mostly carbon dioxide.

But in terms of the environment,

say compared to the surface of Mars,

the clouds of Venus would be a much easier place

to send human beings.

- [Narrator] Let's take a slice of the planet's atmosphere.

From the sweltering ground to the vacuum of space,

200 kilometers tall.

On the surface, you'd feel as squeezed

as diving, nearly a kilometer underwater

and being big twice as hot as in a pizza oven,

But, rise up 50 kilometers,

and you'll enjoy Earth-normal pressure

and springtime temperatures.

This moderate zone, high in the atmosphere,

has plenty of light, but not too much radiation.

It's an ideal location for a research station.

(intriguing electronic music)

Imagine frequent flights into the stormy clouds of Venus.

(thunder rumbling)

The airships would be spun from carbon fiber

harvested from the atmosphere itself,

their electric motors powered by the sun.

Ahead, a permanent floating station, a cloud city awaits.

- I have been thinking of this idea

that you could float habitats in the atmosphere of Venus.

And the habit has could be very large,

they could be kilometers in scale.

And the interesting thing is, if you did this,

you wouldn't even need to have hydrogen or helium

to make them float, because the atmosphere of Venus

is mostly carbon dioxide.

Oxygen and nitrogen, ordinary, breathable air

would float in the atmosphere of Venus.

And inside their giant bubbles,

you can walk around on the inside,

because the air that's holding you up

is also the air that you can breathe.

The lifting gas is your environment.

- [Narrator] The interior ecosystem can be lush

with plenty of room to breathe

and plenty of acreage for growing food.

This home in the clouds can be nearly self-sustaining.

Looking up through the transparent domed rooftop,

you watch vessels come and go.

Suspended beneath the habitat, the logistics hub

to house its core services and computer systems.

The docking ports are staggered across two levels

to accommodate the wide girths of several airships at once.

(propellor buffeting)

(soft orchestral music)

Expeditions set of off, launching instruments as they go.

They'll diverge onto different courses,

running survey transects above the surface of Venus.

- There are some experiments that you could only do

if you actually go and float around in the atmosphere.

And what you could do is answer a lot of the mysteries

that remain about the atmosphere and the clouds.

There's a lot we don't know about what the clouds

are made out of, what kind of chemistry is going on there.

There are gases we call the rare gases:

neon, argon, krypton, xenon.

Or the noble gases, and they're called the noble gases

because they don't react with other gases.

On the periodic table, they're the column

all the way on the right,

and they don't react with anything.

And because of that, they tend to record

longterm aspects of a planet's history,

because they haven't been perturbed by chemistry.

And in addition, there are mysteries of the radiation,

the way solar energy is absorbed and deposited

in the clouds and in the atmosphere

that we would really like to understand,

both to understand Venus,

and also just to round out our understanding

of the way climate works on planets,

which of course is very important to us here on Earth,

struggling with climate change.

There are measurements we would love to do

within the atmosphere of Venus

that could tell us more about the origins

and evolution of that planet.

- [Narrator] The tough balloons will last for many months,

their sensors alert for low-frequency, infrasonic waves.

- Is Venus volcanically active?

Does Venus have plate recycling today?

Those are geophysics questions

that could be answered through seismology,

which we can do from balloon, potentially, by measuring.

This is wonderful, taking advantage of the fact

that the Venus' atmosphere is so thick

that sound waves from earthquakes

will propagate up through the atmosphere

and can be measured from balloon or from orbit.

It's astounding.

- [Narrator] Each science buoy makes a trip around the globe

in about four Earth days.

As they spread out, they form a global network,

performing standoff seismology, meteorology,

atmospheric chemistry, and surface observations.

But if these balloon probes can collect all these data,

why send people all the way to Venus?

- Humans can do things that robots can never do.

That's just a fact.

We can think on the fly, we have hands.

The difficulty of putting hands on another planet,

it's extraordinary.

And link them to a mind.

So, we could ...

with humans in the Venus clouds or in orbit at Venus,

make observations, it would be a telescopic observations,

measurements of chemistry,

or set up an observatory at Venus to study the Venus clouds

and changes that we might expect to be coming

from volcanic and seismic activity at Venus.

So it's the Lando Calrissian model, right? (laughing)

The cloud society at Venus.

We would get more data by having people there.

- Human beings are marvelously versatile,

but human explorers are a lot harder to keep alive

in the atmosphere of Venus.

They need oxygen, they need food, they need sleep.

So I'd love to see human explorers

go to the atmosphere of Venus.

I'd love to see human explorers

that could operate via tele-robotics

some of our high-temperature systems

on the surface of Venus,

so that the humans would be in the atmosphere,

but they're controlling by virtual reality

a system that's on the surface of Venus.

I thought it would be a pretty advanced mission.

That's not something that we're quite ready to do quite yet.

(driving electronic music)

- [Narrator] Success of such missions

will depend on the people who fly them.

No matter how comfortable the cloud community dwellings,

scientists and engineers may only agree to work there

if there is a guarantee of return to Earth.

(rocket roaring)

(curious electronic music)

Habitats in the clouds require energy.

One way to get it is to troll for power:

extend a strong cable from the cold altitude of the dwelling

down into the hot depths of the atmosphere.

But don't let it touch the ground.

The difference in temperature between the cable's top

and bottom can generate electricity,

employing what's known as the Seebeck Effect.

It's an electro thermodynamic device

that needs no moving parts.

(soft orchestral music)

But there may be an even simpler solution,

one that puts no drag on the floating station.

- As you get higher and higher,

as you get above the thickest of the cloud decks

at about 50 kilometers above the surface,

once you get above the cloud decks, it gets very sunny.

It's actually sunnier than the Earth.

It's not ferociously hot, because there's still some amount

of the high cloud that diffuses the light a little bit,

but there's plenty of solar energy.

So I picture the habitats that could float

in the area above the thick clouds of Venus,

probably as being solar powered.

There's plenty of sunlight, the temperature is nice.

Why not pop out your solar panels and run on the sun?

It should work.

(bright orchestral music)

- [Narrator] Solar power on Earth depends on batteries

to store the energy after sunset.

But nighttime on Venus is much longer.

- The surface of Venus rotates very slow and backwards,

so if you were on the surface,

the day-night cycle would be hundreds of days.

But once you get above the surface,

what happens is the clouds

whip around the planet very quickly.

So there's a phenomenon called atmospheric superrotation.

That means that the atmosphere actually rotates

faster than the planet.

So at the Earth-like level, at about 50 to 60 kilometers,

it takes about four days for the winds to circle the planet.

So if you were floating in a balloon or in a habitat

that was just stationary and following the winds,

you'd see about two Earth days of sunlight,

and then you'd have about two Earth days of nighttime.

So when you're talking about power for the habitat,

of course, you would have to provide for power

for the nighttime, and your nighttime's

going to be about two Earth days, but that's not impossible.

You could imagine being solar-powered during the day

and then having enough energy storage

to keep on living and working

and doing whatever you're doing

for your human habitats during the nighttime.

(soft music)

- [Narrator] Like the International Space Station,

a modest-sized floating field station

could support a small group of researchers

for deployments lasting several months.

But, using the same materials and construction techniques,

there's practically no limit

to how big these structures could be built.

(impressive brass music)

Many could cluster together to support a relatively large

group of astronauts over much longer periods.

- I picture the idea of these habitats

as being the size of cities, kilometers in scale.

So I sort of love the idea, and of course,

once you put in one city in the atmosphere of Venus,

why not more, why not 10, why not a 100, why not 10,000?

There's a lot of Venus out there.

- [Narrator] But how safe are these structures?

- Well, the nice thing about the balloons

in the atmosphere of Venus, if they're very, very large,

is that they'd be running with the inside pressure

about the same as the outside pressure.

So it wouldn't be like a space habitat,

say an O'Neill habitat in Earth orbit,

where if you puncture a hole in it,

you get an explosive decompression

and all of the air rushes out.

You'd have the outside air

is about the same pressure as the inside air.

There'd be some exchange of gases.

You wouldn't want that, but it wouldn't burst like a balloon

in a catastrophic failure.

When you have something this big,

it takes a very, very long time to decompress.

If you pop a balloon that's this big,

it's over in an instant,

but when you put a hole in a balloon

that's hundreds of meters across,

it takes a long time to deflate.

And something that's thousands of meters across,

a city, would take days and days

to lose very much atmosphere.

Nevertheless, of course,

I think you'd want to work very hard

to make sure that you don't get those punctures

and you'd make sure that you have multiple

lifting gas areas, so that even if you did,

for one reason or another, have a failure

that made one part of the city lose atmosphere,

the rest of it would have enough lifting gas to hold you up.

- [Narrator] These are large, complex assemblies.

Fortunately, very little of their mass

would have to be hauled here from Earth.

- A lot of the materials

that you could use to build a habitat,

you might be able to make just from the atmosphere of Venus.

It turns out that, in modern engineering,

one of the most versatile, one of the most useful,

materials you can make is carbon fiber.

Carbon fiber is strong. It's lightweight.

You can do a lot with carbon fiber.

But of course, to make a whole city, you need more

than just the structural members of carbon fiber.

So I expect that, if we were making a city,

or 10 cities, or 1,000 cities,

we're probably going to have to go down to the surface

and grab up materials.

So, you will be mining the surface of Venus

to bring up other materials

like the silicon and the silicate rocks

and the lesser materials.

There's a lot you can get out of the atmosphere,

but not everything of course.

What you want to avoid doing as much as possible

is you want to try to avoid

bringing things all the way from Earth,

because the key to living in the solar system

is learning to use the materials that you can find on-hand.

Bringing things up from Earth as a camping trip,

but we don't want to just go camping.

We want to live in the solar system.

(light orchestral music)

- [Narrator] What began with a few

science outposts and airships

could expand into a far flung, interconnected network

of communities beyond Earth.

(gentle percussive music)

The old romantic vision of self-sustaining space settlements

could come alive in the orbit of Venus.

Habitats many kilometers in size

can be constructed from materials

mined from the atmosphere or asteroids,

and they'd be powered by free energy from the nearby sun.

These utopian structures could rotate

to provide comfortable gravity and pleasant weather.

Large ships could dock there,

bringing cargo to be distributed down the gravity well

to the floating towns in Venus's atmosphere.

But the builders of such a city will have to wrestle

with one inevitable design constraint:

most of the mass must be allocated

to sheltering the residents from radiation.

- If we had a colony at the launch points, for example,

we'd probably have to shield them

with many meters of regolith, of dirt.

Well, that's okay. We can mind dirt from the moon.

The moon's got plenty of dirt.

But that's a lot of stuff you have to bring

for no other purpose than hiding away

from the particles coming away from the sun,

galactic cosmic rays coming in from outer space.

- [Narrator] On the other hand, the cloud dwellers

would be safely tucked into the atmosphere.

- Venus does not have a magnetic field to deflect particles,

but it still does have an atmosphere.

So at the level of the middle cloud deck of Venus

and a little bit above,

we're still talking about a lot of atmosphere

between you and space.

So the good thing is that we have enough atmosphere

to attenuate the worst of the radiation.

We're not getting the protons

from the solar flare coronal mass ejections

that would be very, very dangerous,

maybe very deadly for an unprotected human.

We get the 10 tons of atmosphere per square meter

shielding us from the radiation.

Another reason that the clouds of Venus

are a nice place to colonize.

(atmospheric music)

- [Narrator] Venus has nearly the same gravity as Earth.

While it has much more land area, it has no oceans.

What would it take to make the entire planet livable,

to terraform it?

We would have to re-water the whole world.

(atmospheric electronic music)

In the early solar system, the second planet, Venus,

may have been the most hospitable of all,

but as the sun brightened,

Venus struggled to hold on to its oceans.

Carbon dioxide and methane from volcanoes trapped heat,

evaporating the seas.

(steam hissing)

(uncanny music)

Atmospheric water vapor became a greenhouse gas,

holding even more energy from the sun and the planet below.

- Four and a half billion years ago,

Earth's atmosphere was also CO2-rich.

That is, the original atmosphere of the terrestrial planets.

Venus has a very thick carbon dioxide atmosphere today.

And we would, too, if you took all of the carbonate rocks,

the rocks that hold carbon, took all the limestone on Earth,

took Florida, evaporated it back into the sky.

All that carbon dioxide

would be about the equivalent of the carbon dioxide

that's in the Venus atmosphere right now.

- Venus is really off the scale in a sense.

For us to load our atmosphere

with the amount of CO2 that's in Venus's atmosphere

would require us to free up all the carbonate rocks

on our world and get all that carbon

into the atmosphere.

And that would take hundreds and hundreds

of millions of years.

- [Narrator] Space visionaries today

are looking to advanced technologies

to send Venus back in a more Earth-like direction.

- You would have to, obviously, do something

about the very, very strong greenhouse effect.

Maybe you would do that by putting aerosols

into the atmosphere,

filling the atmosphere with dust

long enough to collapse that greenhouse

and get that CO2 to condense out on the surface.

And then you'd have to find some way to keep it condensed,

maybe with, now we're getting science fictional here,

but maybe with orbiting mirrors or something

to cut down on that solar radiation.

- [Narrator] British scientist Paul Birch

proposed transporting trillions of tons of hydrogen

from gas planets such as Jupiter.

The idea is to convert atmospheric CO2 into oceans of water,

plus mountains of graphite.

Birch also suggested shielding Venus from the sun's heat

with enormous, thin panels ...

to cool the atmosphere, shrink its volume ...

and lower its pressure.

(uncanny music)

These giant screens would convert solar energy

to power other terraforming operations ...

like capturing carbon and sealing it underground.

Nobel Prize winner Paul Crutzen

proposed injecting sulfur dioxide into the air

to simulate the dark smoke of gargantuan volcanoes

to cool the surface and tame the greenhouse.

David Grinspoon and Mark Bullock

suggest that exposing native calcium and magnesium

could pull carbon down into carbonate rocks.

(uncanny music)

But where to find a whole planet's worth of water?

- Fortunately, I suppose, if this was your goal,

there's a lot of stray icy objects in the solar system,

the whole outer solar system, the Kuiper Belt,

is loaded with icy objects and would not miss a few of them.

There are literally trillions of icy objects out there.

So if you're imagining some far future

where somebody's got the technical prowess

and the will to do this,

I would take some of these large, icy objects,

some large number of them and crash them into Venus,

which would both raise the dust to collapse the greenhouse

and would return Venus to a more watery condition.

This is not a near-term project. (chuckles)

(frenetic string music)

- [Narrator] To put icy objects on a collision course

with Venus takes delicate orbital mechanics,

a slow-motion ballet of many small robots

with the collective power to move mega mountains.

The swarm distributes itself

according to the unique gravity map of the chosen object.

Choreographed clusters of thruster firings

nudge each massive ice world inbound

onto its own safe trajectory.

The bots may process their captured objects,

separating out water and extracting metals

during their long journey to the inner solar system.

The icy bodies may change shape as materials are mined.

These intelligent machines

might also make clones of themselves

to scale up the operation and get it done faster.

(booming)

When the processed icy asteroids arrive,

they'll be delicately maneuvered into impact speeds

that preserve the most water.

(rumbling)

Dust from the crashes should cut down sunlight,

cooling it quicker.

But smack the planet too hard, and you may unleash hell.

Count on Venus to fight back.

With a thicker crust and no plate tectonics,

Venus doesn't vent its internal heat as easily as Earth.

It builds up.

This world has erupted and repaved its entire surface

at least once in its history

(tense music)

(gentle music)

To remodel an entire planet

seems like the ultimate act of hubris,

but we're already doing it.

- Could we ever terraform Venus and go live on it?

Well, our more immediate task

is to avoid veneraforming Earth right now.

That is, to not turn Earth into Venus

by increasing the greenhouse effect.

So I don't advocate immediately going

and trying to live on Venus or Mars

and trying to terraform them

to escape from our problems here.

However, the mental exercise of imagining

how we would terraform another planet,

I think, is very valuable for our task

of learning how to manage ourselves on Earth better,

because it forces us to ask,

how would we interact constructively with the planet?

How would we intentionally alter a planet's climate

and manage a planet's climate

as opposed to unintentionally and inadvertently

messing with a planet's climate

as we've been doing here on Earth?

- I think actually learning to live in the solar system

is going to teach us ways to help us live on Earth.

What we call pollution on the Earth,

on the moon we'd call that valuable resources.

That's gonna help us live on Earth,

just understanding that an ecosystem is a closed cycle.

There is no such thing as waste.

All of the waste has to be recycled and come back.

- [Narrator] On the other hand,

learning the techniques to better manage Earth

might just give us the tools

to tackle living on or around other worlds.

It might take decades, centuries, millennia ...

but our distant descendants may well be born

into a solar system with more than one place to call home.

Some may be in the clouds of atmospheres.

(soft piano music)

Some may orbit freely.

Still others might live on the surfaces of worlds.

- I think we should move out into the solar system,

and I really want to go everywhere.

I want to put human beings at the poles of Mercury.

I want to go to Venus. I want to go to Mars.

I think we should go into the outer solar system

and start looking at some of the resources

of the Kuiper belt.

I think human beings can, and we should,

settle the whole solar system,

- [Narrator] As it was when the planets first formed,

Earth's twin made beckoned us to its shores.

(building orchestral music)

(intriguing instrumental music)